/Engine/Source/Runtime/Core/Public/Math/UnrealMathUtility.h
Interpolate quaternion from Current to Target. Scaled by angle to Target, so it has a strong start speed and ease out.
template<class T> static [UE::Math::TQuat](API\Runtime\Core\Math\TQuat)< T > QInterpTo ( const [UE::Math::TQuat](API\Runtime\Core\Math\TQuat)< T > & Current, const [UE::Math::TQuat](API\Runtime\Core\Math\TQuat)< T > & Target, float DeltaTime, float InterpSpeed )